class Solution {
public:
    int minDistance(string word1, string word2) {
        int m = size(word1);
        int n = size(word2);
        vector<vector<int>> dp(m + 1, vector<int>(n + 1));
        for (int i = 1; i <= m; ++i)
        {
            dp[i][0] = i;
        }
        for (int i = 1; i <= n; ++i)
        {
            dp[0][i] = i;
        }
        for (int i = 1; i <= m; ++i)
        {
            for (int j = 1; j <= n; ++j)
            {
                int r = (word1[i - 1] == word2[j - 1]) ? dp[i - 1][j - 1] : dp[i - 1][j - 1] + 1;
                int d = dp[i - 1][j] + 1;
                int u = dp[i][j - 1] + 1;
                dp[i][j] = min(d, min(r, u));
            }
        }
        return dp[m][n];
    }
};